Meditation and Sleep schedule

Is it possible for a person to have sleeping disorders or problems with large durations of meditation? I know a few very big siddhas that have astonishing powers and they meditate up to 8 hours a day after office hours and sleep for 4 hours only. When I tried a long duration of meditation, I found a lack of sleepiness, and my sleep schedule was a bit altered. Is there any possibility of a large duration of deviation through meditation? What is the best way to manage that?